1. Field of the Invention
The present general inventive concept relates to an ion neutralizer, and, more particularly, to an ion neutralizer comprising a reflection plate to neutralize plasma ions in a semiconductor processing plasma apparatus.
2. Description of the Related Art
In semiconductor processing, plasma has been widely used for various unit processes, such as physical or chemical vapor deposition, photosensitive agent cleaning, and other surface processes. According to demands on high integration of a semiconductor device and an increase in a wafer diameter or area, requirements for an apparatus for processing an object also become strict, which is the same as those for plasma equipment. In an attempt to enhance performance of the plasma equipment, it has been developed for the plasma equipment to perform high speed processing by increasing a density of the plasma within a chamber, or to perform processing of an object having a large area by providing uniform plasma distribution. For example, a density of the plasma can be increased by inductively coupled plasma equipment, and the uniform plasma distribution can be provided by displacement of an antenna or variation of introducing location of reactant gas.
However, in spite of the above attempt, the plasma processing has a limitation in performing super accuracy processing of wafers. For example, if charged plasma ions are used for an etching process, an object of the etching process can also be charged during the etching process, thereby changing an etching profile or creating a voltage gradient and causing damage to a diode formed on the object. Meanwhile, when accelerated plasma ions are used for the etching process, dislocations or deformed skin layers can be formed on a surface of a substrate. In order to solve these problems, energy of the plasma ions must be lowered, or additional heat treatment must be performed to restore the damaged surface of the object after the etching process.
In order to solve the disadvantages of the plasma processing as described above, U.S. Pat. No. 4,662,977 discloses a method using neutralized particles instead of the plasma ions in a conventional ion neutralizer. According to the disclosure, the plasma ions generated from a plasma generator are transformed into the neutralized particles after being reflected by heavy metal plates, so that the neutralized particles are used for processing an object. Processing equipment using the above method requires an ion neutralizer for neutralizing the plasma ions. However, the conventional ion neutralizer has various disadvantages, and thus the disadvantages of the conventional ion neutralizer should be overcome to improve the plasma processing.
The conventional ion neutralizer has a construction as follows.
The conventional ion neutralizer comprises a ring-shaped frame defining an outer periphery of the ion neutralizer, and a plurality of reflecting plates arranged in parallel inside the frame. The frame is formed with a refrigerant path for cooling heat generated upon impact of plasma ions, and a plurality of slots for inserting the reflection plates within a diameter of the frame. Each reflecting plate is inserted at both ends thereof into the slots, and fixed thereto. When the plasma ions collide with the reflecting plates, the plasma ions are subjected to charge exchange, and are then transformed into neutralized particles.
When the plasma ions collide with the reflecting plates, heat of the plasma ions is transferred to the reflecting plates, increasing a temperature of the reflecting plates. The heat is transferred to the frame, and is then finally discharged to an outside thereof via the refrigerant passing through the refrigerant path in the frame. Meanwhile, if the heat transfer between the reflecting plates and the frame is not smoothly performed, the reflecting plates have a remarkably increased temperature, and are subjected to thermal deformation, causing the reflecting plates to be bent. When the reflection plates are bent, a direction of the neutralized particles reflected by the reflection plates is deviated from a designed direction, negatively influencing the result of the process.
In the conventional ion neutralizer, since the frame and the reflecting plates are provided by machining metallic materials, some degree of surface roughness is necessarily formed on the surfaces of the frame and the reflecting plates, so that when the reflecting plates are inserted into the slots of the frame, a plurality of point contacts are created between the reflecting plates and the frame. As a result, since the heat transfer between the reflecting plates and the frame is mainly carried out through these point contacts, a heat transfer rate is remarkably lowered. Particularly, since the interior of the plasma equipment where the ion neutralizer is installed is generally in a vacuum state, there are no media, which can improve the heat transfer between the reflecting plates and the frame, thereby deteriorating a heat transfer rate therebetween.